Plugging port hole in Sierra 2 center that's in a cabinet?

I'm going to resurrect this thread with a twist. I've tried to find all references to effective use of S2 (and S1) in enclosed environments or close to a wall. I've tried to read all references to use of the Q-Plugs, A and B, in S1 and S2 (and the Towers!). I'd like to wrap up my understanding, and ask for confirmation, here.

I'm reinstalling my S2s at the outer ends of two bookcases, left and right, with the TV between the the bookcases. Distance to listening position is not important here. Unlike my previous use of these S2s in this room, I now have a Rythmik F8 sub to go with them. AND, I bought Q-Plug kits. I am driving it all with a Denon AVR-X6200W, so I have choice of crossover characteristics, levels and distances, but I am not using room EQ for now. The primary use is 2-channel TV sound, with movies, and music, all at moderate listening levels. I seek the best from the S2s, integrated with the F8. That possibly includes a second order high-pass slope, rather than the 4th order that it has, unplugged. The backsides of the S2s are firing into a corner, as shown below for the left speaker. There is about 1" of clearance above the S2.
Attachment 1660

The question is: Q-Plug A or B in this case? And then, how deep to insert them: until they are flush with the back of the S2 (probably not); or much deeper, until they are flush with the end of the port tube, where the flare starts.

Thanks.